Which term is generally defined as a decrease in the number of white blood cells?

The term that denotes a decrease in the number of white blood cells is leukopenia. This condition is characterized by a lower-than-normal count of leukocytes (white blood cells), which can impair the body's ability to fight infections and can be indicative of various underlying health issues, including infections, bone marrow disorders, or the effects of certain medications.

Leukocytosis, in contrast, refers to an increase in the number of white blood cells, often in response to infection or inflammation. Neutrophilia specifically indicates an increase in neutrophils, a type of white blood cell, usually linked to acute stress or infection. Pancytopenia encompasses a reduction in all three blood cell types: red blood cells, white blood cells, and platelets, rather than just white blood cells, making it a broader term that does not specifically define a decrease in leukocytes alone.